Cathode cup construction



y 1949- z. J. ATLEE 2,471,298

CATHODE CUP CONSTRUCTION Filed 001;. 2, 1943 INVENTOR.

Patented May 24 1949 UNITED STATES PATENT OFFICE CATHODE CUPCONSTRUCTION Application October 2, 1943, Serial No. 504,742

Claims.

This invention relates in general to electron fiow and particularly tothe control of the fiow of electrons and the focusing of them upon theanode target of an X-ray generator.

An important object of the present invention is to provide means forcausing electrons to flow in predetermined paths from an electron sourceso as to focus them upon the anode target of an X-ray generator in themanner generally described in United States Letters Patent No.2,316,214, granted April 13, 1943, for operation in industrialradiography at Voltages of the order of 200 kilovolts and higher. Inthose operations it is frequently desirable to use tubes of relativelysmall physical dimensions. In such cases, when a plurality of electronemissionelements is used, it is necessary to partition the filaments ofthe cathode by material of a higher melting point than the iron or coldrolled steel of which the cathode cup described in those Letters Patentis usually made.

A further important object of this invention, therefore, is to providemeans in a cathode cup structure for controlling the flow of electronsto provide line focus focal spots, of the order of 5 millimeters indiameter, more or less, during such high voltage operations.

Another important object of this invention is to provide a metaldividing strip between the filaments of a cathode cup structure for thegeneration of electrons in an X-ray tube of relatively small physicaldimensions for high voltage operation so as to enable electrons to befocused upon a target area in line focus focal spots of the order offive millimeters in diameter and smaller.

This invention further resides in the combination, construction andarrangement of parts illustrated in the accompanying drawings, and whilethere is shown therein preferred embodiments of the invention, it is tobe understood that the same are susceptible of modification and changewithout departing from the spirit of the invention.

The accompanying drawings illustrate a selected embodiment of theinvention, and the views therein are as follows:

Fig, 1 is a side elevation of an illustrative embodiment of theinvention;

Fig. 2 is a central vertical sectional view of a portion of the deviceshown in Fig. *1;

Fig. 3 is an end view of the portion of the device shown in Fig. 2,looking to the left in that figure;

Fig. 4 is a detail perspective view of a portion of the device shown inFigs. 2 and 3;

Fig. 5 is a sectional view along the line 5-5 of Fig. 4;

Fig. 6 is a sectional view along the line 6-6 of Fig. 5;

Fig.7 is an enlarged detail perspective view of a portion of the deviceshown in Fig. 4.

The illustrative embodiment of the invention shown in the drawingscomprises an X-ray generator I I having a cathode l2, and an anode [3,of

' any usual or preferred form, supported within a sealed evacuatedenvelope H.

The cathode i2 comprises a cup shaped element I5 having a fiat bottom l6and generally cylindrical walls I! defining a cavity I8 opening towardthe anode l3. The side walls and bottom of the cup, instead of beingformed integrally as shown in the above mentioned Letters Patent,comprise separate parts, preferably made of cold rolled steel, thesidewalls being secured in one end of a tubular cathode body l9 by meansof screws 20. In other respects, including predetermined diameter todepth ratio, the structure of the cup is as described in the abovementioned Letters Patent.

The electron emitting source comprises a plurality of parallel filaments2 I. The filaments are arranged in an enlarged portion or pocket 22 of adiametrically extending slot 23 provided in the bottom I6 of the cup [5.The pocket 22 is generally centrally located, as shown in Fig. 3.

The slot 23 is arranged to receive a metallic strip 24, preferably madeof molybdenum, tantalum, or tungsten, which have a high melting point,and having'a central portion 25 of increased width or height. The edgesof the slot 23 adjacent one end of the strip 24 are solidly peened overthe adjacent portion of the strip, as indicated at 26 in Figs. 4 and 5,tightly to anchor that end of the strip in the slot. The edges of theslot 23 adjacent the opposite end of the strip 24 are lightly peenedover the adjacent portion of the strip, as indicated at 21 in Figs. 4and 6, to keep the strip within: the slot but permitting longitudinalmovement of that portion of the strip upon expansion thereof whenheated. To this end the strip 24- is slightly shorter in length than theslot 23 so as to avoid buckling of it upon expansion.

The portion 25 of the strip 24 serves not only in assisting in thefocusing of electrons emitted by the filaments 2| but in partitioningthe heatgenerated upon their being energized throughleads 28, 29. Forproviding a focal spot of the order of five millimeters in diameter theportion 25 may extend about ten one-thousandths (0.010) of an inchoutwardly from the bottom 16 of the cup l5. If a focal spot of greatermagnitude be desired, this dimension will be increased and the filamentraised. If a focal spot of less magnitude be desired, this dimensionwill be reduced and the filament depressed.

Changes may be made in the form, construction and arrangementof theparts without departing from the spirit of the invention, and the rightis hereby reserved to make all such changes as fairly fall within thescope of the following claims.

The invention is hereby claimed as follows:

1. An electronic device embodying an anode and a cooperating cathodecomprising an electron guiding member forming a cup providing .a cavityhaving an opening facing said anode, and a closed bottom having a slotforming a pocket, a plurality of elongated electron emission elementsdisposed in side by side, spaced apart relationship in said pocket, atthe bottom of said cavity, and a partition comprising a strip of metalex- I tending between an adjacent pair of said emission elements, saidpartition having a 'medial portion extending in said pocket and end"1301'- tions supported in sockets comprising grooves formed in saidbottom of the cup at and. opening intothe opposite ends of said pocket,said end portions being retained in said sockets by peened portions ofsaid bottom at the edges of said grooves.

2. An electronic device embodying ananode and a cooperating cathodecomprising a disc forming an electron guiding member, said .disc havingan elongated pocket formed inthe. surface thereof facing said anode, aplurality of elongated electron emission elements disposed in side byside spaced apart relationship in said pocket, said plate being formedwith relatively narrow grooves at the opposite ends of said pocket andin alignment with the medial axis thereof, and a partition comprising astrip of metal extending between an adjacent pair of said emissionelements, said partition having a medial portion extending in saidpocket and end portions mounted in said grooves.

3. An electronic device embodying an anode and a cooperating cathodecomprising a disc forming an electron guiding member, said disc havingan elongated pocket formed in the surface thereof facing said anode, aplurality of elongated electron emission elements disposed in side byside spaced apart relationship in said pocket, said plate being formedwith relatively narrow grooves at the opposite ends of said pocket andin alignment with the medial axis thereof, anda partition comprising astrip of metal extending between an adiacent pair of said emissionelements, said partition having a medial portion extending in saidpocket and end portions mounted in said grooves, at least one of saidend portions of the partition being free to move in its supportinggroove, in a longitudinal direction to accommodate expansion of thepartition when heated.

4. An electronic device embodying an anode and a cooperating cathodecomprising a disc forming an electronic guiding member, said disc havingan elongated pocket formed in the surface thereof facing said anode, aplurality of elongated electron emission elements disposed in side byside spaced apart relationship in said pocket, said plate being formedwith relatively narrow grooves atthe opposite ends of said pocket and inalignment with the medial axis thereof, said grooves extending outwardlyof the opposite ends of the pocket and having outer ends opening at themarginal surfaces of the disc, and a partition comprising a strip ofmetal extending between an adjacent pair of said emission elements, saidpartition having a' medial portion extending in said pocket and endportions mounted in said grooves, and a sleeve member having a skirtportion snugly embracing the marginal surfaces of the disc in positionoverlying the outer ends of said grooves.

5. An electronic device embodying an anode and "a cooperating. cathodecomprising a disc forming an electronic guiding member, said disc havingan elongated pocket formed in the surface thereof facing saidanode, aplurality of elongated electron emission elements disposed in side byside spaced apart relationship in said pocket, said plate being formedwith relatively narrow grooves at the opposite ends of said pocket andin align- .ment with the medial axis thereof, said grooves extendingoutwardly of the opposite ends of the pocket and having outer endsopening at the marginal surfaces of the disc,'and a partition comprisinga strip of metal extending between an adjacent pair "of said emissionelements, said partitionhaving a medial portion extending in said pocketand end portions mounted in said grooves, anda sleeve member having askirt portion snugly embracing the marginal surfaces of the disc inposition overlying the outer ends of said grooves, said grooves,inwardly of the marginal edges of the disc, opening on the surface gotthe disc facing said anode, and said sleeve having a shoulder inposition engaging the anode facing surface of the disc at the marginaledge thereof in position overlying said grooves.

ZED J. ATLEE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

